Evaluation of Mechanical Activity on Knee Extensor Muscles under Isometric Contraction by MC Sensor Method

Abstract

This study aimed to investigate the mechanical activity of the knee extensor muscles under isometric contraction with different muscle length conditions. Subjects were 11 healthy men. The knee extensor torque under isometric contraction with hip joint angles of 0° and 90° and knee joint angles of 30°, 60° and 90° was measured using a dynamometer. Integrated electromyography （iEMG）, an indicator of the electrical activity of knee extensor muscles, was measured by surface electromyography; pressure on the target muscle, as an indicator of mechanical activity, was measured using a muscle contraction （MC） sensor. Results showed that iEMG was significantly higher in knee flexion than in knee extension, while the MC ended to be higher in knee extension than in knee flexion. In particular, the knee joint angle strongly influenced the MC value of the vastus medialis oblique. High linearity between torque and MC value was also seen for all conditions. From these results, it was suggested that the MC value can evaluate the mechanical activity of the muscle, and clarify that the MC value indeed reflects the intensity of torque at different muscle lengths.